1. Field of the Invention
This invention relates to an outboard motor, particularly to a hybrid outboard motor equipped with an internal combustion engine and an electric motor which are used as power sources for driving a propeller.
2. Description of the Related Art
Hybrid outboard motors adapted for mounting on a boat and equipped with an engine and a motor used as power sources for driving a propeller have been developed in a variety of types, as taught, for example, by Japanese Laid-Open Utility Model Application No. Sho 63(1988)-158493, particularly FIGS. 1 and 4.
In such an outboard motor, an electronic control unit or controller for controlling the operation of either or both of the engine and the motor is, as shown in Japanese Laid-Open Patent Application No. Hei 10(1998)-37780, particularly FIG. 3, installed on the outboard motor, namely, inside the outboard motor.
Owing to the fact that the engine installed in the outboard motor generates vibration and heat, the mounting structure of the electronic control unit and the devices used in its electronic circuitry have to be made capable of withstanding vibration, heat and other harsh environment conditions. The electronic control unit therefore becomes complex in structure and high in cost. In addition, installation of the electronic control unit inside the outboard motor is inconvenient because the limited interior space of the outboard motor leaves little mounting layout freedom.